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<?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX This file is generated from xml source: DO NOT EDIT XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX --><title>prefork - Apache HTTP Server</title><link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /><link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /><link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link href="../images/favicon.ico" rel="shortcut icon" /></head><body><div id="page-header"><p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p><p class="apache">Apache HTTP Server Version 2.0</p><img alt="" src="../images/feather.gif" /></div><div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div><div id="path"><a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="../">Version 2.0</a> > <a href="./">Modules</a></div><div id="page-content"><div id="preamble"><h1>Apache MPM prefork</h1><div class="toplang"><p><span>Available Languages: </span><a href="../de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |<a href="../en/mod/prefork.html" title="English"> en </a> |<a href="../es/mod/prefork.html" hreflang="es" rel="alternate" title="Espa駉l"> es </a> |<a href="../ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p></div><table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Implements a non-threaded, pre-forking web server</td></tr><tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr><tr><th><a href="module-dict.html#ModuleIdentifier">Module營dentifier:</a></th><td>mpm_prefork_module</td></tr><tr><th><a href="module-dict.html#SourceFile">Source燜ile:</a></th><td>prefork.c</td></tr></table><h3>Summary</h3> <p>This Multi-Processing Module (MPM) implements a non-threaded, pre-forking web server that handles requests in a manner similar to Apache 1.3. It is appropriate for sites that need to avoid threading for compatibility with non-thread-safe libraries. It is also the best MPM for isolating each request, so that a problem with a single request will not affect any other.</p> <p>This MPM is very self-regulating, so it is rarely necessary to adjust its configuration directives. Most important is that <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> be big enough to handle as many simultaneous requests as you expect to receive, but small enough to assure that there is enough physical RAM for all processes.</p></div><div id="quickview"><h3 class="directives">Directives</h3><ul id="toc"><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#acceptmutex">AcceptMutex</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#bs2000account">BS2000Account</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#enableexceptionhook">EnableExceptionHook</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#group">Group</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listen">Listen</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listenbacklog">ListenBacklog</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#lockfile">LockFile</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxclients">MaxClients</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxmemfree">MaxMemFree</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li><li><img alt="" src="../images/down.gif" /> <a href="#maxspareservers">MaxSpareServers</a></li><li><img alt="" src="../images/down.gif" /> <a href="#minspareservers">MinSpareServers</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#pidfile">PidFile</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#serverlimit">ServerLimit</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#startservers">StartServers</a></li><li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#user">User</a></li></ul><h3>Topics</h3><ul id="topics"><li><img alt="" src="../images/down.gif" /> <a href="#how-it-works">How it Works</a></li></ul><h3>See also</h3><ul class="seealso"><li><a href="../bind.html">Setting which addresses and ports Apacheuses</a></li></ul></div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div><div class="section"><h2><a name="how-it-works" id="how-it-works">How it Works</a></h2> <p>A single control process is responsible for launching child processes which listen for connections and serve them when they arrive. Apache always tries to maintain several <dfn>spare</dfn> or idle server processes, which stand ready to serve incoming requests. In this way, clients do not need to wait for a new child processes to be forked before their requests can be served.</p> <p>The <code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code>, <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>, <code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code>, and <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> regulate how the parent process creates children to serve requests. In general, Apache is very self-regulating, so most sites do not need to adjust these directives from their default values. Sites which need to serve more than 256 simultaneous requests may need to increase <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code>, while sites with limited memory may need to decrease <code class="directive"><a href="../mod/mpm_common.html#maxclients">MaxClients</a></code> to keep the server from thrashing (swapping memory to disk and back). More information about tuning process creation is provided in the <a href="../misc/perf-tuning.html">performance hints</a> documentation.</p> <p>While the parent process is usually started as <code>root</code> under Unix in order to bind to port 80, the child processes are launched by Apache as a less-privileged user. The <code class="directive"><a href="../mod/mpm_common.html#user">User</a></code> and <code class="directive"><a href="../mod/mpm_common.html#group">Group</a></code> directives are used to set the privileges of the Apache child processes. The child processes must be able to read all the content that will be served, but should have as few privileges beyond that as possible.</p> <p><code class="directive"><a href="../mod/mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></code> controls how frequently the server recycles processes by killing old ones and launching new ones.</p></div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div><div class="directive-section"><h2><a name="MaxSpareServers" id="MaxSpareServers">MaxSpareServers</a> <a name="maxspareservers" id="maxspareservers">Directive</a></h2><table class="directive"><tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle child server processes</td></tr><tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareServers <var>number</var></code></td></tr><tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxSpareServers 10</code></td></tr><tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr><tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr><tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr></table> <p>The <code class="directive">MaxSpareServers</code> directive sets the desired maximum number of <em>idle</em> child server processes. An idle process is one which is not handling a request. If there are more than <code class="directive">MaxSpareServers</code> idle, then the parent process will kill off the excess processes.</p> <p>Tuning of this parameter should only be necessary on very busy sites. Setting this parameter to a large number is almost always a bad idea. If you are trying to set the value lower than <code class="directive"><a href="#minspareservers">MinSpareServers</a></code>, Apache will automatically adjust it to <code class="directive">MinSpareServers</code><code> + 1</code>.</p><h3>See also</h3><ul><li><code class="directive"><a href="#minspareservers">MinSpareServers</a></code></li><li><code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code></li></ul></div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div><div class="directive-section"><h2><a name="MinSpareServers" id="MinSpareServers">MinSpareServers</a> <a name="minspareservers" id="minspareservers">Directive</a></h2><table class="directive"><tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle child server processes</td></tr><tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareServers <var>number</var></code></td></tr><tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MinSpareServers 5</code></td></tr><tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr><tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr><tr><th><a href="directive-dict.html#Module">Module:</a></th><td>prefork</td></tr></table> <p>The <code class="directive">MinSpareServers</code> directive sets the desired minimum number of <em>idle</em> child server processes. An idle process is one which is not handling a request. If there are fewer than <code class="directive">MinSpareServers</code> idle, then the parent process creates new children at a maximum rate of 1 per second.</p> <p>Tuning of this parameter should only be necessary on very busy sites. Setting this parameter to a large number is almost always a bad idea.</p><h3>See also</h3><ul><li><code class="directive"><a href="#maxspareservers">MaxSpareServers</a></code></li><li><code class="directive"><a href="../mod/mpm_common.html#startservers">StartServers</a></code></li></ul></div></div><div class="bottomlang"><p><span>Available Languages: </span><a href="../de/mod/prefork.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> |<a href="../en/mod/prefork.html" title="English"> en </a> |<a href="../es/mod/prefork.html" hreflang="es" rel="alternate" title="Espa駉l"> es </a> |<a href="../ja/mod/prefork.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p></div><div id="footer"><p class="apache">Copyright 1995-2005 The Apache Software Foundation or its licensors, as applicable.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p><p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div></body></html>⌨️ 快捷键说明
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